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# transfer::copy(n) 0.2 tcllib "Data transfer facilities"

## Name

transfer::copy - Data transfer foundation

## Synopsis

- package require Tcl 8.4
- package require transfer::copy ?0.2?

- transfer::copy::do chan|string data outchannel ?options...?
- transfer::copy::chan channel outchannel ?options...?
- transfer::copy::string string outchannel ?options...?
- transfer::copy::doChan channel outchannel optvar
- transfer::copy::doString string outchannel optvar
- transfer::copy::options outchannel optionlist optvar

## Description

This package provides a number of commands for the asynchronous of information contained in either a string or channel. The main point of this package is that the commands here provide a nicer callback API than the builtin command fcopy, making the use of these facilities simpler than the builtin.

## API

transfer::copy::do chan|string data outchannel ?options...?

  This command transfers the information in data to the outchannel, according to the options. The type of the information in data is determined by the first argument.

  The options available to this command are the same as are available to the command transfer::copy::options, and explained there.

  chan

    The argument data contains the handle of a channel and the actual infomration to transfer is read from that channel.

  string

    The argument data contains a string and this is the information to be transfered.

transfer::copy::chan channel outchannel ?options...?

  This command is a shorter and more direct form for the command transfer::copy::do chan.

transfer::copy::string string outchannel ?options...?

  This command is a shorter and more direct form for the command transfer::copy::do string.

transfer::copy::doChan channel outchannel optvar

  This command is an alternate form of transfer::copy::chan which reads its options out of the array variable named by optvar instead of from a variable length argument list.

transfer::copy::doString string outchannel optvar

  This command is an alternate form of transfer::copy::string which reads its options out of the array variable named by optvar instead of from a variable length argument list.

transfer::copy::options outchannel optionlist optvar

  This command is the option processor used by all the commands above which read their options from a variable length argument list. It first reads default settings from the channel handle outchannel, then processes the list of options in optionlist, at last stores the results in the array variable named by optvar. The contents of that variable are in a format which is directly understood by all the commands above which read their options out of an array variable.

  The recognized options are:

  -blocksize int

    This option specifies the size of the chunks to transfer in one operation. It is optional and defaults to the value of -buffersize as configured for the output channel.

    If specified its value has to be an integer number greater than zero.

  -command commandprefix

    This option specifies the completion callback of the operation. This option has to be specified. An error will be thrown if it is not, or if the empty list was specified as argument to it.

    Its value has to be a command prefix, i.e. a list whose first word is the command to execute, followed by words containing fixed arguments. When the callback is invoked one or two additional arguments are appended to the prefix. The first argument is the number of bytes which were transfered. The optional second argument is an error message and added if and only if an error occured during the the transfer.

  -progress commandprefix

    This option specifies the progress callback of the operation. It is optional and defaults to the empty list. This last possibility signals that no feedback was asked for and disabled it.

    Its value has to be a command prefix, see above, -command for a more detailed explanation. When the callback is invoked a single additional arguments is appended to the prefix. This argument is the number of bytes which were transfered so far.

  -size int

    This option specifies the number of bytes to read from the input data and transfer. It is optional and defaults to "Transfer everything". Its value has to be an integer number and any value less than zero has the same meaning, i.e. to transfer all available data. Any other value is the amount of bytes to transfer.

    All transfer commands will throw error an when their user tries to transfer more data than is available in the input. This happens immediately, before the transfer is actually started, should the input be a string. Otherwise the, i.e. for a channel as input, the error is thrown the moment the underflow condition is actually detected.

  -encoding encodingname
  -eofchar eofspec
  -translation transspec

    These options are the same as are recognized by the builtin command fconfigure and provide the settings for the output channel which are to be active during the transfer, and only then. I.e. the settings of the output channel before the transfer are saved, and restored at the end of a transfer, regardless of its success or failure. None of these options are required, and they default to the settings of the output channel if not specified.

## Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category transfer of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.

## Keywords

channel, copy, transfer

## Category

Transfer module

## Copyright

Copyright © 2006-2009 Andreas Kupries <andreas_kupries@users.sourceforge.net>